This invention relates to electrophotographic imaging and, more particularly, relates to separate replaceable cartridges for toner and photoconductor, which are pressed together for good operation when installed in the imaging device.
Electrophotographic toner cartridges are often joined in two sections pivoted to one another so that a developer roller can be pressed against a photoconductor drum with controlled pressure. The controlled pressure is provided by permanently installed springs stretching between the two sections. The two sections are not normally separated, so such cartridges can be said to be one part cartridges.
Such one part cartridges have the advantage of having the spring force installed at the factory manufacturing the cartridge and having a relatively short duration during which the springs need provide the correct pressure, since the entire cartridge is refurbished (or discarded) after use of the original cartridge. Such one-piece cartridges have the disadvantage that the springs must be included on each cartridge. Also, for such one piece cartridges, replacement of the toner with a new section having the toner is not practical since the sections are not readily separated.
Two part cartridges are known in which a part having the toner is readily separated from a part having the photoconductor drum, since they are not pivoted to one another. To install such two part cartridges for imaging, they are manually brought together by the operator, and then the operator activates a latching mechanism, such as a resilient latch or a lever of some kind, to force the two parts together with the appropriate pressure for imaging.
A disadvantage of such known two part cartridges is that the forcing mechanism must be on one or both of the two parts and therefore adds to supplies costs, as both of the two parts are typically replaceable as they are worn (in the case of the photoconductor and other physical parts) or expended (in the case of the toner). Another disadvantage is that operator involvement requires training or some skill, and requires an overall design which permits the operator to reach the latching mechanism and activate it or deactivate it. A further disadvantage is that the force biasing elements require some space in the body of the imaging devide.
This invention provides for two part cartridges which have no mechanism to latch the cartridges together. Biasing force during use is provided from the cover of the imaging device when closed. The two parts need only have conforming external configurations so that they fit together, and require no space in the middle of the printer for a force biasing element. No operator involvement in forcing the two parts together is required except for inserting the cartridges in the imaging device and closing the cover of the imaging device. Although the biasing by the cover may be by a spring or springs more costly than springs or other forcing mechanism which might be on the parts, over the life of the imaging device the overall costs typically will be less.